This invention relates to a wheel for a pneumatic tire and more particularly to a wheel designed to minimize bead unseating during the use of the tire, especially in the uninflated state.
Bead retention has always been considered an important aspect of tire and wheel design. However, with the advent of run-flat safety tires, tires which are capable of being driven in the uninflated state for an extended distance, bead retention has become of even greater importance. When a tire is run in the uninflated state, there is a strong tendency for the bead portion of the tire to unseat from the rim of the wheel, which can present serious hazards to the safety of the occupants of the vehicle, and/or possibly cause damage to the tire itself.
It is well known to augment bead retention by some form of projection which extends radially outward from the bead seat between the tire bead and the wheel well so as to engage the toe of the bead to restrict axial displacement of the bead into the wheel well as is exemplified by U.S. Pat. Nos. 3,669,174; 2,409,666; 1,652,146; 3,664,405; and German DAS 2,363,175. Due to high cornering forces, such projections are usually insufficient to retain the bead in its seat when the tire is run in the uninflated condition. Additionally, projections such as exemplified in the above patents pose certain difficulties in mounting and demounting a tire from the wheel, therefore making automatic mounting and demounting impractical. Furthermore, the use of a localized projection may cause damage to a bead bundle due to stresses imposed upon it during use in the uninflated condition. It is also well known to provide a substantially continuous circumferential ridge around the rim as exemplified in U.S. Pat. No. 2,198,978. Safety humps such as this must of necessity be of relatively low profile so as not to project radially outwardly substantially above the surface of the rim seat. Otherwise, the safety rib would make it too difficult to mount the tire on the rim seats.